Female gametogenesis and early seed development in Amaranthus hypochondriacus L.

Abstract

<p><strong>Background</strong>: Attention to amaranth grains has increased in recent years due to the nutritional value of their seed proteins, which have high levels of the amino acid lysine. However, there is no detailed study describing the stages of seed development in <em>Amaranthus hypochondriacus. </em></p><p><strong>Question</strong>: How are the developmental patterns of the female gametophyte and young seed in <em>Amaranthus hypochondriacus</em>?</p><p><strong>Species studied</strong>: <em>Amaranthus hypochondriacus</em> L ’Revancha’ (Amaranthaceae).</p><p><strong>Study site and years of study</strong>: Plants were growth and collected from 2014 to 2016, in a greenhouse at Instituto Tecnológico de Celaya, Guanajuato, Mexico.</p><p><strong>Methods: </strong>Glomerules were collected before pollination and two weeks after anthesis. The ovules at different development stages were fixed and cleared and were analyzed by light microscopy. A clearing protocol was used to observe the developmental stages during female gametogenesis and embryogenesis.</p><p><strong>Results: </strong>We observed that the <em>Amaranthus hypochondriacus</em> ovule has a campylotropous form. The female gametophyte showed a<em> Polygonum</em>-type pattern of development. We were also able to identify all the stages from the megaspore mother cell to the cotyledon embryo stage. After meiosis, the micropylar megaspore differentiates into the functional megaspore. The embryo did not show symmetric divisions, although the final pattern is similar to that of in eudicotyledons. The suspensor showed additional longitudinal divisions, giving rise to a 2-rowed suspensor, while the endosperm showed a helobial development.</p><p><strong>Conclusions: </strong>These results will be used as baseline to identify morphological changes during seed development and to develop new strategies to improve seed quality or increase the yield.</p>